Defrosting apparatus for an absorption refrigerator



B. A. PHILLIPS ETAL 3,063,257

I Nov. 13, 1962 DEFROSTING APPARATUS FOR AN ABSORPTION REFRIGERATOR Filed Nov. 13, 1959 2 Sheets-Sheet l INVENTORQ Nov. 13, 1962 B. A. PHILLIPS ETAL 3,063,257

DEFROSTING APPARATUS FOR AN ABSORPTION REFRIGERATOR Filed Nov. 13, 1959 2 SheetsSheet 2 Patented Nov. 13., 1962 free DEFROSTING APPARATUS FOR AN ABSORPTION REFRIGERATOR Benjamin A. Phillips, John Roeder, Jr., and Roy W. Kruggel, Benton Harbor, Mich., assignors to Whirlpool Corporation, a corporation of Delaware Filed Nov. 13, 1959, Ser. No. 852,876 11 Claims. (Cl. 62-275) This invention relates to a defrosting apparatus for a refrigeration evaporator and particularly to such an evaporator used in an absorption refrigeration system.

One of the features of this invention is to provide an improved defrosting apparatus in which means are provided for heating a refrigerant and means are provided for conducting this heated refrigerant into heat exchange relationship with the evaporator to defrost the evaporator.

Another feature of the invention is to provide such a defrosting apparatus in which a reservoir of liquid refrigerant is maintained at all times and refrigerant from this reservoir is periodically heated and vaporized and conveyed to the evaporator for achieving said defrosting.

A more specific feature of the invention is to provide such an apparatus in which means are included for removing moisture from the refrigerant in the reservoir.

Other features and advantages of the invention will be apparent from the following description of certain embodiments thereof taken in conjunction with the accompanying drawings. Of the drawings:

FIGURE 1 is a fragmentary elevational view of a portion of an absorption refrigeration system partially broken away for clarity of illustration and illustrating one embodiment of the invention.

FIGURE 2 is an enlarged sectional elevational view of one portion of the apparatus of FIGURE 1.

FIGURE 3 is a view similar to FIGURE 1 but illustrating a second embodiment of the invention.

The refrigeration system illustrated herein is generally similar to that shown, described and claimed in the copending application of Benjamin A. Phillips, Serial No. 778,370 filed December 5, 1958 and assigned to the same assignee as is the present invention. In the accompanying drawings only those portions of the system are shown that are necessary to illustrate the invention.

In the embodiment of FIGURES 1 and 2 there is provided a relatively low temperature first evaporator tube 10, a relatively higher temperature second evaporator tube 11, both inclined to the horizontal, a heat exchanger tube 12 also inclined to the horizontal and connecting substantially vertical tubes 13 and 14 to connect all tubes in series. There is also provided a pipe 15 for inert gas leading from an absorber (not shown) extending interiorly of a connector'tube 16 also leading to the absorber. The pipe 15 is located on the interior of tubes to 14 and 16 in heat exchange relationship therewith. The portion of the pipe within the evaporators is provided with radially extending inclined fins 17 as shown diagrammatically in FIGURE 1. The extreme upper end of the pipe 15 is provided with a downwardly extending extension 18 having its extreme outer end 19 open and bent downwardly.

Leading from an ordinary refrigerant condenser (not shown) is a pipe 20 for liquid refrigerant. As is illustrated this pipe is attached to the exterior surfaces of the heat exchanger tube 12 and the vertical tube 14 in order to be cooled by the surfaces. The pipe 20 then extends upwardly to connect to the upper bottom surface of the first evaporator tube 10. Thus the pipe 20 conveys liquid refrigerant into the evaporator sections and serves to precool the refrigerant during its passage.

As can be seen, the refrigeration system illustrated here is of the uniform pressure absorption type in which an inert gas or auxiliary pressure equalizing fluid is employed. In such a system the refrigerant may be ammonia, the inert gas may be hydrogen and the absorption liquid may be water, which will thereby form a solution with the ammonia refrigerant. In such a system a generator is used to boil oif ammonia gas from a liquid rich in dissolved ammonia. The ammonia gas is then conveyed to a condenser where it is condensed to a liquid form before being conveyed into the evaporator for subsequent evaporation and cooling. Thus in the illustrated embodiment here, the hydrogen gas flows up through the pipe 15 to the extreme upper end of the evaporator 10. The liquid refrigerant from the pipe 20 also enters at this end and the liquid refrigerant evaporates into the hydrogen to produce the cooling effect.

The mixture of liquid refrigerant, gas refrigerant and hydrogen flows by gravity down through the first evaporator 1(). The remaining liquid refrigerant then flows down through a connecting pipe 21 to the upper end of the second evaporator 11. The gas refrigerant and hydrogen flow down through the tube 13 into the second evaporator 11. The liquid refrigerant from the pipe 21 flows down the second evaporator 11 and evaporates therein into the mixed atmosphere of hydrogen and gaseous refrigerant. From the lower end of the second evaporator 11 liquid refrigerant flows down through a pipe 22 into an accumulator chamber 23. The liquid refrigerant pipe 22 is connected to the chamber 23 at an inlet 24. The chamber 23 is inclined downwardly from this inlet 24 and is connected to a pipe 25 at an outlet 26 from the chamber 23. This pipe 25 is provided with :1 depending loop 27 providing a reservoir having a lower portion 28. One leg 29 of the loop extends from this lower portion 28 upwardly to empty into the top of the upper portion 38 of the first evaporator 10. The leg 29 adjacent the lower portion 28 is provided with an electric heater 31 for heating the contents of the loop 27 at the lower end of the leg 29.

The accumulator chamber 23 is provided with another pipe 32 having an inlet end 33 above the chamber inlet 24. Pipe 32 empties into the upper end of the heat exchanger 12. Liquid refrigerant flowing through the pipe 32 into the heat exchanger 12 then evaporates within the heat exchanger 12 into the atmosphere of mixed hydrogen and gaseous refrigerant. The resulting rich mixture of refrigerant and hydrogen then flows down through the connector tube 16 into the absorber (not shown).

Located within the upper end 30 of the evaporator 10 is a substantially hemispherical dish 34 having a small opening 35 adjacent its bottom. The dish 34 is located beneath the inner end 36 of the leg 29 and the outer end 19 of the inert gas pipe extension 18 extends within the dish 34 to beneath the upper edge thereof. The adjacent end of the gas pipe 15 is provided with a small opening 37 for bleeding the inert gas at all times from this pipe into the interior of the evaporator 10.

At a normal refrigerating operation of the apparatus the inert gas, hydrogen, flows upwardly through the pipe 15 and empties by way of the extension 18 into the upper end 30 of the first evaporator 10. Some of the liquid refrigerant from the pipe 20 evaporates into the inert atmosphere within the evaporator 10 while the remainder of the liquid refrigerant flows down the inside of the evaporator 10 to the lower end thereof and from this end through the pipe 21 into the upper end of the second evaporator 11. In the meantime mixed inert gas and gaseous refrigerant flows from the evaporator 10 down into the vertical tube 13 and the second evaporator 11.

Liquid refrigerant from the pipe 21 entering the upper end of the second evaporator 11 evaporates into the gaseous atmosphere in the evaporator 11 to produce further refrigerating effect. The remaining liquid refrigerant flows down the bottom of the second evaporator 11 to the lower end thereof and then through the pipe 22, chamber 23 and pipe 32 into the upper end of the heat exchanger 12. Mixed inert gas and refrigerant gas flows from the evaporator 11 down through the tube 14 into the heat exchanger 12. Liquid refrigerant from the pipe 32 evaporates into this atmosphere and the resulting relatively rich gas then flows down through the tube 16 to the absorber (not shown).

Liquid refrigerant from the chamber 23 flows into the pipe 25 and the loop 27. The liquid level in the system made up of the pipes 22, 25, 27, 29 and 32 and the chamber 23 is determined by the level of the end 38 of the pipe 32 where it empties into the heat exhcanger 12. This liquid level line is indicated in FIGURE 1 at 39.

When it is desired to defrost the evaporators the electric heater 31 is energized either manually or by a timer. When a timer is used the defrosting occurs generally once every 24 hours. The heat generated by the heater 31 vaporizes some of the liquid refrigerant in the tube leg 29 which thereupon becomes a lift tube. Then by gas-lift action the hot mixture of liquid refrigerant and gaseous refrigerant is lifted upwardly in the pipe 29 into the evaporator 10. This hot mixture flowing out the inner end of the pipe 29 first separates into liquid and vapor, and the liquid substantially fills the dish 34 and then flows down through the evaporators and 11 to warm them and remove frost therefrom. The substantial filling of the dish 34 with the hot liquid refrigerant blocks the end 19 of the inert gas pipe extension 18 to reduce substantially the flow of inert gas. Thus a liquid seal is provided to stop gas flow through the main passage 19. A limited gas flow continues through opening 37. This limited gas flow mixing with the vapor entering at 36 results in a gas of high ammonia concentration. The ammonia dew point of this gas is to be well above 32, so that ammonia condensing out of the gas will warm the tubing above 32 thus defrosting the evaporators.

As the refrigeration system continues to operate, either because the usual thermostat switch is usually mounted adjacent the evaporator circuit and has been warmed up or because it was operating at the beginning of the defrost cycle, liquid refrigerant continues to be supplied through the pipe 20. This together with the ammonia condensing in the cold tubes serves to replenish the refrigerant in the accumulator chamber 23, the pipe 25, and the loop 27.

At the end of the defrost cycle which is customarily about to minutes, the electric heater 31 is deenergized. Shortly after this the supply of vapor and heated liquid through the leg 29 by the gas-lift pumping action is stopped. Liquid within the dish 34 then drains out the opening 35 to break the liquid seal at the outer end 19 of the gas pipe 15 and permit the inert gas to resume its normal flow. The refrigeration system thereupon operates in its normal manner.

During the normal refrigeration cycle the lower end of pipe 22 and pipe 25, loop 27, pipe 32 and accumulator chamber 23 will be filled with liquid refrigerant containing some water up to the liquid level as indicated by the line 39. Thus there is always a stored amount of predominantly liquid refrigerant available at all times in preparation for the defrost cycle. During the defrosting there is provided a closed circuit from heater 31, through the leg 29 and evaporators 10 and 11 and through the pipes 22 and and accumulator 23 into the loop 27. Thus everything beneath the liquid level 39 serves as a reservoir for liquid refrigerant for use during the defrosting cycle. During the defrosting any gaseous refrigerant that does not condense in the defrosting operation eventually flows gack to the absorber and the generator (not shown).

At the time of first start-up of a refrigeration system utilizing the present invention, there may be a surplus of water within the accumulator 23. Since a solution having an excess amount of water has a substantially higher boiling point, it is desirable to remove the water quickly, The heavier water solution tends to settle in the lower end of accumulator 23, but the refrigerant entering the accumulator from pipe 22 is caused to bubble up through the water, which action carries the water solution out with the ammonia refrigerant passing up through accumulator 23 and out through pipe 32.

In the second embodiment shown in FIGURE 3, identical numerals are used on identical parts. In this embodiment, as in the first embodiment, inert gas flows into the system through the pipe 16 and liquid refrigerant flows into the system through the pipe 20. The refrigerant and gas mixture then flows down the circuit including the first evaporator 10, tube 13, second evaporator 11, tube 14 and heat exchanger 12. In this embodiment, however, the liquid refrigerant for defrost purposes is taken from the lower end of the first evaporator 10 by way of a pipe instead of from the lower end of the second evaporator 11 by way of the pipe 22 as shown in the first embodiment. The pipe 40 connects to the upper end of downwardly inclined accumulator chamber 41 and from a lower end of this chamber a pipe 42 conveys liquid refrigerant to the upper end of the second evaporator 11. A pipe 43 conveys liquid refrigerant from the lower end of the second evaporator 11 to the upper end of the heat exchanger 12.

A pipe 44 extends from the accumulator 41 at a level above the accumulator end of the pipe 42 and connects to a downwardly extending loop 45 similar to the loop 27 of the first embodiment and also provides with an upwardly extending leg 46 that connects to the upper end 30 of the first evaporator 10.

In the second embodiment the heavier entrained water and liquid refrigerant tends to flow toward the lower end of the inclined accumulator chamber 41. From here it flows through the pipe 42 into the upper end of the second evaporator 11. The lighter refrigerant entering through pipe 40 then will substantially float on the heavier liquid inthe accumulator chamber 41, and by means of piston action actually forces the heavier liquid out through pipe 42 and pipe 44. Experimental results indicate this method of purging the system of water is much faster than that obtained with the structure shown in FIGURE 1.

Another advantage of the second embodiment of FIG- URE 3 is that the liquid refrigerant is taken from the first or freezer evaporator 10 and placed in the defrost circuit so that the defrost circuit is always supplied with refrigerant in liquid form up to approximately the liquid level indicated by the line 47, regardless of the cooling demand on the system. In the embodiment of FIGURE 1 the liquid refrigerant is not fed into the defrost circuit until it reaches the lower end of the second evaporator I l. This means that if the demand for cooling has been excessive so that there has been an abnormally high evaporation of liquid refrigerant there may be little or no refrigerant left in liquid form by the time it reaches the end of the evaporator 11 and the entrance to the defrost circuit feeder pipe 22.

In the defrosting system of this invention the vaporized heated refrigerant supplies the majority of the defrost heat. However, the heated liquid also supplies heat for defrosting. As the heated refrigerant vapor is carried through the evaporator system by the gas flow, it condenses on any area which is at low temperature or is held there by external frost accumulation. The condensed refrigerant then flows back to the defrost storage chamber. During this time the normal refrigeration process is supplying additional liquid refrigerant to make up for that which does not condense in the evaporators and is carried out to the absorber by the gas flow. Thus substantially no refrigeration has taken place during this time because of the reduction in the flow of inert gas. The sensible heat in the liquid refrigerant and in the weak gas aids in the defrosting process.

Although in both illustrated embodiments an electric heater 31 is shown other methods of supplying heat such as by gas burner or a transfer system relaying heat from the generator to the pumping system may be used. The defrosting system of this invention operates with whatever heat is applied to leg or pump tube 46. Defrosting occurs regardless of the operational status of the unit at the time of the defrosting cycle. It is very desirable, however, that the refrigerator system be operating at full imput during the defrosting cycle. This will insure continuous supply of liquid refrigerant to the defrosting system.

Having described our invention as related to the embodiments shown in the accompanying drawings, it is our intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

We claim:

1. In a refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into said evaporator with said liquid refrigerant normally evaporating into said gas within the evaporator to produce refrigeration, defrosting apparatus, comprising: a conduit leading to said evaporator including a reservoir for maintaining a supply of liquid refrigerant; means for periodically heating said liquid refrigerant in the reservoir; means for expelling said heated refrigerant in the form of both liquid and gas into the evaporator for causing defrosting of said evaporator by the heat of said heated refrigerant; receiving means in said evaporator for receiving said heated liquid refrigerant to form a pool having a maximum level, said inert gas conduit outlet being located beneath said maximum level to be blocked by said pool for substantially reducing said normal evaporation during defrost ing; means for permitting restricted gas flow from said conduit into the evaporator during said blocking; and means for draining said pool at the conclusion of said heating preparatory to restoring said normal evaporation.

2. In a refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into said evaporator with said liquid refrigerant normally evaporating into said gas within the evaporator to produce refrigeration while said liquid refrigerant is flowing from one level downstream in said system, defrosting apparatus, comprising: a conduit extending from said one level to a lower level and receiving liquid refrigerant at said lower level including a reservoir for maintaining a supply of liquid refrigerant; means for periodically heating said liquid refrigerant in the reservoir; means for expelling said heated refrigerant in the form of both liquid and gas into the evaporator for causing defrosting of said evaporator by the heat of said heated refrigerant, receiving means in said evaporator for receiving said heated liquid refrigerant to form a pool having a maximum level, said inert gas conduit outlet being located beneath said maximum level to be blocked by said pool for substantially reducing said normal evaporation during defrosting; means for permitting restricted gas flow from said conduit into the evaporator during said blocking; and means for draining said pool at the conclusion of said heating preparatory to restoring said normal evaporation.

3. In a refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptiying into said evaporator with said liquid refrigerant normally evaporating into said 6 gas Within the evaporator to produce refrigeration while said liquid refrigerant is flowing from one level downstream in said system, defrosting apparatus, comprising: a conduit extending from said one level to a lower level and receiving liquid refrigerant at said lower level, the conduit including a depending loop forming a reservoir having a lower portion in which liquid refrigerant is maintained; means forming an accumulator chamber in said conduit between said lower level and said lower portion, the chamber thereby having an inlet receiving liquid from said lower level and an outlet leading to said reservoir lower portion; an outlet conduit leading from said chamber to said system at an area downstream from said lower level for conveying liquid refrigerant back to said system; means for periodically heating said liquid refrigerant in the loop at an area between said lower portion and said one level simultaneously to heat the liquid and expel the heated liquid refrigerant into the evaporator at said one level for defrosting the same; receiving means in said evaporator for receiving said heated liquid refrigerant to form a pool having a maximum level, said inert gas conduit outlet being located beneath said maximum level to be blocked by said pool for substantially reducing said normal evaporation during defrosting; means for permitting restricted gas flow from said conduit into the evaporator during said blocking; and means for draining said pool at the conclusion of said heating preparatory to restoring said normal evaporation.

4. The apparatus of claim 3 wherein said outlet conduit has an inlet end within said chamber above the level of said chamber inlet.

5. The apparatus of claim 3 wherein said outlet conduit has an inlet end at said chamber beneath said chamber outlet.

6. In an absorption refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into the evaporator, defrosting apparatus, comprising: a conduit leading to said evaporator including a reservoir for maintaining a supply of liquid refrigerant; means for periodically heating said refrigerant in the reservoir; means for flowing said heated liquid refrigerant into the evaporator for defrosting the same; means forming a liquid seal with said flowing heated liquid refrigerant during said defrosting for blocking said inert gas outlet; and means for continuing limited flow of inert gas from said conduit into said evaporator during said blocking of said outlet.

7. In an absorption refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into the evaporator, defrosting apparatus, comprising: a conduit leading to said evaporator including a reservoir for maintaining a supply of liquid refrigerant; means for periodically heating said refrigerant in the reservoir; means for expelling said heated liquid refrigerant into the evaporator for defrosting the same; a sump for said heated liquid refrigerant communicaing with said evaporator, the outlet of the inert gas conduit being closed when the sump contains a predetermined amount of said heated liquid refrigerant and the sump including means for removing liquid therefrom subsequent to said defrosting; and means for continuing limited flow of inert gas from said conduit into said evaporator during said blocking of said outlet.

8. In an absorption refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into the evaporator, defrosting apparatus, comprising: a conduit leading to said evaporator including a reservoir for maintaining a supply of liquid refrigerant; means for periodically heating said refrigerant in the reservoir; means for expelling said heated liquid refrigerant into the evaporator for defrosting the same; and a sump within the evaporator for receiving said heated liquid, the outlet of the inert gas conduit extending into said sump to be substantially blocked by said heated liquid refrigerant in the sump when the sump contains a predetermined amount of said liquid, the gas conduit including means for conveying inert gas therefrom to the evaporator at a reduced rate when said gas outlet is thereby blocked by said liquid and the sump including means for removing liquid therefrom subsequent to said defrosting 9. In an absorption refrigeration system including an evaporator having an inlet for liquid refrigerant and a conduit for inert gas having an outlet emptying into the evaporator, the gas thereby normally flowing into the evaporator and the refrigerant evaporating into the gas to provide refrigeration while the refrigerant flows from one level downstream in said system, defrosting apparatus, comprising: a conduit extending from said one level to a lower level and receiving liquid refrigerant at said lower level, the conduit including a depending loop forming a reservoir having a lower portion in which liquid refrigerant is maintained; means forming an accumulator chamber in said conduit between said lower level and said lower portion, an outlet conduit leading from said chamber to said system at an area downstream from said lower level for conveying liquid refrigerant back to said system; means for periodically heating said liquid refrigerant in the loop at an area between said lower portion and said one level simultaneously to heat the liquid and expel the heated liquid refrigerant into the evaporator at said one level for defrosting the same; and a sump within the evaporator for receiving said heated liquid refrigerant, the outlet of the inert gas conduit extending into said sump to be substantially blocked thereby when the sump contains a predetermined amount of said liquid, the gas conduit including means for conveying inert gas therefrom to the evaporator at a reduced rate when said gas outlet is thereby blocked by said liquid and the sump including means for removing liquid therefrom subsequent to said defrosting.

10. In an absorption refrigeration system including an evaporator, a conduit for liquid refrigerant having an outlet emptying into the evaporator and a conduit for inert gas having an outlet emptying into the evaporator, defrosting apparatus, comprising: a conduit for hot liquid refrigerant having an outlet emptying into the evaporator during a defrost cycle for defrosting the evaporator; means within said evaporator forming a liquid seal with said hot liquid refrigerant blocking said inert gas outlet during said defrosting; and means for continuing limited flow of inert gas from said conduit into said evaporator during said blocking of said outlet.

11. In an absorption refrigeration system including an evaporator, a conduit for liquid refrigerant having an outlet emptying into the evaporator and a conduit for inert gas having an outlet emptying into the evaporator, defrosting apparatus, comprising: a conduit for hot liquid refrigerant having an outlet emptying into the evaporator during a defrost cycle for aid in defrosting the evaporator; a sump in the evaporator receiving said hot liquid refrigerant, said outlet of the inert gas conduit extending into said sump to be substantially blocked thereby when the sump contains a predetermined amount of said liquid; and means forming a second outlet from said gas conduit emptying into the evaporator at all times.

References Cited in the file of this patent UNITED STATES PATENTS 1,970,340 Ruff Aug. 14, 1934 2,468,104 Phillips Apr. 26, 1949 2,630,685 Lewis Mar. 10, 1953 2,670,606 Hainsworth Mar. 2, 1954 2,670,607 Hainsworth Mar. 2, 1954 2,738,653 Berry Mar. 20, 1956 2,769,311 Duncan Nov. 6, 1956 2,999,368 Schomburg Sept. 12, 1961 

